NEAR OPTIMUM DETECTION IN SYNCHRONOUS CODE-DIVISION MULTIPLE-ACCESS SYSTEMS

Communication networks employing code division multiple access include applications where several packets of information are transmitted synchronously and simultaneously over a common channel. In this paper, we consider the problem of simultaneously demodulating every packet from such a transmission. A nonlinear detection scheme based on a linear complexity multistage multiple-access interference rejection algorithm is studied. A class of linear detectors are considered as constituting the first stage for the multistage detector. A bit-error probability comparison of the linear and multistage detectors is undertaken. It is shown that the multistage detectors are capable of achieving considerable improvements over the linear detectors, particularly in near-far situations, i.e., in the demodulation of weak signals in the presence of strong interfering signals. This problem has been of primary concern for currently operational CDMA systems. Higher bandwidth utility factors are also achieved by the use of such detectors as will be demonstrated by some representative examples.